There may only be two female northern white rhinos left alive, but there is still hope the ‘doomed’ species could come back from the brink of extinction.
For the first time, scientists have managed to create hybrid embryos of the northern white rhino (NWR) — the world’s most endangered mammal.
Researchers have successfully developed rhinoceros embryos to the blastocyst stage, which means they are ready for implantation in a surrogate.
The last male northern white rhino, Sudan, died in Kenya at the age of 45 in March.
Scroll down for video
The world’s last male northern white rhino, Sudan, died in Kenya at the age of 45 in March. For the first time researchers have successfully developed rhinoceros embryos to the blastocyst stage — potentially ready for implantation
Researchers led by Dr Thomas Hildebrandt from the Leibniz Institute for Zoo and Wildlife Research have created hybrid rhinoceros embryos and derived stem cells from these using in vitro fertilisation, or IVF.
To create the lab-grown embryo, researchers used thawed sperm from previously frozen northern white rhino males.
Given the dwindling number of available northern white rhino female eggs (oocytes), researchers fertilised eggs from a closely related subspecies, the southern white rhinoceros (SWR).
The resulting hybrid NWR‒SWR embryos developed to the blastocyst stage.
These successful embryos have been frozen for possible implantation into surrogate southern white rhinoceros females in the future.
The next challenge will be to transfer the frozen embryos to the surrogate mothers to establish and carry the pregnancy to term.
Researchers also plan to harvest eggs from the two living female NWRs.
The study ‘raises hopes that genes from the functionally extinct northern white rhino subspecies can be conserved,’ researchers said.
Experts had worried resurrecting the subspecies using frozen cells could create a heavily inbred population.
However, research from May suggested that the species has enough diversity in its DNA to survive this ‘genetic bottleneck’.
There may only be two northern white rhinos (pictured) left alive, but scientists say there is hope yet to bring the ‘doomed’ mammals back from the brink of extinction
HOW DO SCIENTISTS HOPE TO SAVE THE NORTHERN WHITE RHINO USING IVF?
Scientists are hoping to use IVF and stem cell techniques developed for humans to resurrect the northern white rhino – but the process is fraught with challenges
While the death of Sudan marks a symbolic turning point in the fight to save the northern white rhino, in fact the survival of the species has been entirely reliant on untested IVF techniques for years.
It was hoped that Sudan, his daughter Najin and granddaughter Patu might be able to produce offspring when they were moved to Kenya in 2009, but their close genetic relationship rendered them infertile.
Since at least 2015 scientists have been working with IVF and stem cell techniques in the hopes of being able to create a viable northern white rhino embryo, according to a GoFundMe page for the project.
Researchers in Berlin and San Diego are using DNA samples collected from a dozen northern whites, including Sudan, and trying to apply techniques developed for humans to the animal.
If a viable embryo can be created, it would then have to be implanted into the womb of a southern white rhino, since Majin and Patu will likely be dead before the technique is perfected.
While the southern white rhino would be responsible for giving birth to the baby, because the infant’s genetic material came solely from northern whites, it would be a member of that species.
However, as Save The Rhino points out, the process is fraught with difficulty and has a low chance of success.
In the last 15 years just 10 rhino births have resulted from artificial insemination and only two embryos have ever been created – one of which divided into two cells before perishing, and the other one into three.
For the northern white rhino to be genetically viable a minimum of 20 healthy individuals must be born – meaning the whole process must be successfully completed 20 times – to avoid inbreeding.
Then, it would be necessary to find a suitable habitat for them, since their old habitat has largely been destroyed and led the species to the brink of extinction in the first place.
During such a bottleneck, only a small number of animals contribute to the gene pool, which leads to a weaker species that struggles against disease outbreaks and environmental changes.
The closely-related SWR recovered from near-extinction itself, following a sharp drop in numbers driven by poaching and habitat destruction.
In the early 20th century the subspecies was world’s most endangered rhino with just 20 left alive, however, there are now more than 20,000 living in the wild.
Scientists said the northern white could make a similar recovery through conservation efforts that make use of frozen cell lines.
The world’s last male northern white rhino, Sudan, is survived by just two females – his daughter Najin and granddaughter Fatu.
In vitro fertilization is used in the cattle industry to breed more robust herds, and a Cape buffalo was conceived through IVF for the first time in 2016.
Sudan was survived by just two females – his daughter Najin (left) and granddaughter Fatu (right). Semen from dead northern white rhinos is stored in various locations around the world, and the result provides hope for those looking to resurrect the northern white
Supporters believe the work could be used to help other endangered species, while some conservationists believe the focus should be on other critically endangered species, including the Javan and Sumatran rhinos, that have suffered because of poaching and human encroachment on habitats.
Northern white rhinos were particularly vulnerable because of conflicts that swept their central African range.
The last ones in the wild were observed more than a decade ago in Congo’s Garamba National Park, a frequent target of well-armed poachers.
The ‘much-hyped’ plan for rhino in vitro fertilization is probably too late to save the northern white subspecies, according to Save the Rhino, a London-based group. Pictured is Sudan, the world’s last male northern white, shortly before he died in March
The ‘much-hyped’ plan for rhino in vitro fertilization is probably too late to save the northern white subspecies, according to Save the Rhino, a London-based group.
‘With small chance of healthy new calves, and limited place in their historic range to go, Save the Rhino believes that the best outcome will be to put our efforts and funding – including research into IVF – into saving the species which do still have a chance,’ it said on its website.
‘The real fight for the survival of northern white rhinos in their natural habitat was lost over a decade ago,’ Jo Shaw, African rhino expert with the WWF conservation group, told the Associated Press in March.
‘Large mammals, like rhinos, should be seen as symbols of large functioning ecosystems and we must focus our efforts and energy on their protection and ongoing survival within these vital landscapes around the globe.’
In this image, wildlife ranger Zachariah Mutai takes care of Sudan, the world’s last male northern white rhino, at the Ol Pejeta Conservancy in Laikipia county in Kenya. The 45-year-old rhino died in March, leading many to believe the northern white rhino was doomed